使用AOF持久化文件实现还原Redis数据库并得到RDB持久化文件

目录

1 编写本文的初衷

2 具体实施

2.1 Redis持久化概念简介

2.2 获取指定Redis的AOF持久化文件

2.3 把Redis的持久化AOF文件转换为RDB文件

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1 编写本文的初衷

因为目前实习工作需求，需要把服务器环境中所有Redis数据进行初步简单分析，即统计其中存储的每一个key所占内存的大小，以便作出清理不重要缓存数据的决策。

但是，由于从线上环境获得持久化文件为AOF文件，而不是RDB文件。RDB文件可以通过Rdbtools工具，来分析具体数据。但是AOF文件不能这样操作。

因此，就给我带来一个问题：如何通过AOF文件获取指定的RDB持久化文件呢？

于是，我通过查阅网上文章，获取的一个解决思路：单独在Redis中开启一个未使用过的端口服务，使用已得到的AOF文件替换该端口服务下自动生成的AOF文件；然后，重启该端口指定的Redis服务，即可把新的AOF文件中数据加载到Redis数据库中，最后在该端口服务客户端执行save或者bgsave命令，即可在指定路径下得到对应的RDB持久化文件。

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2 具体实施

2.1 Redis持久化概念简介

Redis数据库进行持久化有两种方式：RDB持久化和AOF持久化。

那么，什么是RDB持久化呢？

RDB(Redis Database)持久化：可以将Redis在内存中的数据库状态保存到磁盘里面，避免数据意外丢失。RDB持久化既可以手动执行，也可以根据服务器配置选项定期执行，该功能可以将某个时间点上的数据库状态保存到一个RDB文件中。（PS：手动执行保存时，在客户端执行SAVE命令或者BGSAVE即可把当前所有数据保存到dump.rdb文件中,如果在线上执行，建议使用BGSAVE命令）

RDB文件具体功能：用于保存和还原Redis服务器所有数据库中的所有键值对数据。

那么，什么是AOF持久化呢？

AOF(Append Only File)持久化:与RDB持久化通过保存数据库中的键值对来记录数据库状态不同，AOF持久化是通过保存Redis服务器所执行的写命令来记录数据库状态的。AOF持久化功能的实现可以分为命令追加（append）、文件写入、文件同步（sync）三个步骤。

AOF文件具体功能：通过保存所有修改数据库的写命令请求来记录服务器的数据库状态。

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2.2 获取指定Redis的AOF持久化文件

一般情况，都是获取限制环境的AOF文件，那么如何在线上环境找到AOF文件呢？（PS：因为时间原因，可能忘记存储在哪里，所以以下提供一个搜索命令，方便操作）

sudo find / -name '*.aof'   # 此命令用于查找系统上所有以aof为后缀的文件 

通过该命令，查看具体文件的路径信息，即可确认自己需要获取的AOF文件。

确定后，通过一下命令把指定AOF文件拷贝到本地主机上：

scp liuzhen@172.160.12.16:/home/liuzhen/prod_redis_data/redis/redis-appendonly.aof . # 从服务器复制远程文件到本地当前所在根目录

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2.3 把Redis的持久化AOF文件转换为RDB文件

关于redis.conf文件中配置aof持久化操作信息简单介绍：

(1)找到redis.conf文件，设置其中的字段属性：

appendonly no ——> appendonly yes

此处也可以在redis客户端，使用指令来完成修改：

redis 127.0.0.1:6379> config set appendonly yes  
 
OK  
 
redis 127.0.0.1:6379> BGREWRITEAOF   # 用于重写生成aof文件
 
Background append only file rewriting started

此选项为aof功能的开关，默认为“no”，可以通过“yes”来开启aof功能

只有在“yes”下，aof重写/文件同步等特性才会生效

(2)在redis.conf文件中，指定aof文件的名称

appendfilename "appendonly.aof"  # 这是文件中默认的配置名称，也可以自己修改指定的文件名称

(3)在redis.conf文件中，确认 aof操作中文件同步策略

配置默认结果：

# appendfsync always
 
appendfsync everysec
 
# appendfsync no

即选用everysec，具体意思：

1. no:表示等操作系统进行数据缓存同步到磁盘.

2. always:表示每次更新操作后手动调用fsync() 将数据写到磁盘.

3. everysec:表示每秒同步一次.一般用everysec

（4）在redis.conf文件中，确认 aof-rewrite期间，appendfsync是否暂缓文件同步

配置默认结果：

no-appendfsync-on-rewrite no

具体意思：

"no"表示“不暂缓”，“yes”表示“暂缓”，默认为“no”

（5）在redis.conf文件中，确认 aof文件rewrite触发的最小文件尺寸(mb,gb),以及 相对于“上一次”rewrite，本次rewrite触发时aof文件应该增长的百分比

配置默认结果：

auto-aof-rewrite-percentage 100
 
auto-aof-rewrite-min-size 64mb

具体实施步骤：

(1) 创建一个新的redis.conf文件，该文件命名可采用redis_port.conf形式，例如：redis_6391.conf。该文件中内容起初完全何Redis默认的redis.conf文件中内容一致

(2) 修改redis_6391.conf指定的port值，在文件中搜索port把默认的6379修改为6391

(3) 修改redis_6391指定的dir值，在文件中搜索dir把默认的".\"改为自己要存放文件的具体路径。该路径用于存放RDB文件和AOF文件

(4) 修改redis_6391指定的appendfilename值，在文件中搜索appendfilename把默认的"appendonly.aof"改为自己想要定义的文件名称，该文件即为AOF文件的最终名称

(5) 修改redis_6391指定的dbfilename值，在文件中搜索dbfilename把默认的"dump.rdb"改为自己想要定义的文件名称，该文件即为RDB文件的最终名称

(6) 此步骤最重要，修改redis_6391指定的appendonly值，在文件中搜索appendonly把默认的"no"改为"yes"。这句配置意思是Redis服务重启后，默认不加载AOF持久化文件恢复数据，而是去找RDB持久化文件恢复；如果修改为"yes"后，发现有AOF文件，会首先加载AOF文件恢复数据

以下给出我本机修改后的redis_6391.conf文件中具体配置代码：

 # Redis configuration file example
 
 # Note on units: when memory size is needed, it is possible to specify
 # it in the usual form of 1k 5GB 4M and so forth:
 #
 # 1k => 1000 bytes
 # 1kb => 1024 bytes
 # 1m => 1000000 bytes
 # 1mb => 1024*1024 bytes
 # 1g => 1000000000 bytes
 # 1gb => 1024*1024*1024 bytes
 #
 # units are case insensitive so 1GB 1Gb 1gB are all the same.
 
 ################################## INCLUDES ###################################
 
 # Include one or more other config files here.  This is useful if you
 # have a standard template that goes to all Redis server but also need
 # to customize a few per-server settings.  Include files can include
 # other files, so use this wisely.
 #
 # Notice option "include" won't be rewritten by command "CONFIG REWRITE"
 # from admin or Redis Sentinel. Since Redis always uses the last processed
 # line as value of a configuration directive, you'd better put includes
 # at the beginning of this file to avoid overwriting config change at runtime.
 #
 # If instead you are interested in using includes to override configuration
 # options, it is better to use include as the last line.
 #
 # include /path/to/local.conf
 # include /path/to/other.conf
 
 ################################ GENERAL  #####################################
 
 # By default Redis does not run as a daemon. Use 'yes' if you need it.
 # Note that Redis will write a pid file in /var/run/redis.pid when daemonized.
 daemonize no
 
 # When running daemonized, Redis writes a pid file in /var/run/redis.pid by
 # default. You can specify a custom pid file location here.
 pidfile /var/run/redis.pid
 
 # Accept connections on the specified port, default is 6391.
 # If port 0 is specified Redis will not listen on a TCP socket.
 port 6391
 
 # TCP listen() backlog.
 #
 # In high requests-per-second environments you need an high backlog in order
 # to avoid slow clients connections issues. Note that the Linux kernel
 # will silently truncate it to the value of /proc/sys/net/core/somaxconn so
 # make sure to raise both the value of somaxconn and tcp_max_syn_backlog
 # in order to get the desired effect.
 tcp-backlog 511
 
 # By default Redis listens for connections from all the network interfaces
 # available on the server. It is possible to listen to just one or multiple
 # interfaces using the "bind" configuration directive, followed by one or
 # more IP addresses.
 #
 # Examples:
 #
 # bind 192.168.1.100 10.0.0.1
 # bind 127.0.0.1
 
 # Specify the path for the Unix socket that will be used to listen for
 # incoming connections. There is no default, so Redis will not listen
 # on a unix socket when not specified.
 #
 # unixsocket /tmp/redis.sock
 # unixsocketperm 700
 
 # Close the connection after a client is idle for N seconds (0 to disable)
 timeout 0
 
 # TCP keepalive.
 #
 # If non-zero, use SO_KEEPALIVE to send TCP ACKs to clients in absence
 # of communication. This is useful for two reasons:
 #
 # 1) Detect dead peers.
 # 2) Take the connection alive from the point of view of network
 #    equipment in the middle.
 #
 # On Linux, the specified value (in seconds) is the period used to send ACKs.
 # Note that to close the connection the double of the time is needed.
 # On other kernels the period depends on the kernel configuration.
 #
 # A reasonable value for this option is 60 seconds.
 tcp-keepalive 0
 
 # Specify the server verbosity level.
 # This can be one of:
 # debug (a lot of information, useful for development/testing)
 # verbose (many rarely useful info, but not a mess like the debug level)
 # notice (moderately verbose, what you want in production probably)
 # warning (only very important / critical messages are logged)
 loglevel notice
 
 # Specify the log file name. Also the empty string can be used to force
 # Redis to log on the standard output. Note that if you use standard
 # output for logging but daemonize, logs will be sent to /dev/null
 logfile ""
 
 # To enable logging to the system logger, just set 'syslog-enabled' to yes,
 # and optionally update the other syslog parameters to suit your needs.
 # syslog-enabled no
 
 # Specify the syslog identity.
 # syslog-ident redis
 
 # Specify the syslog facility. Must be USER or between LOCAL0-LOCAL7.
 # syslog-facility local0
 
 # Set the number of databases. The default database is DB 0, you can select
 # a different one on a per-connection basis using SELECT <dbid> where
 # dbid is a number between 0 and 'databases'-1
 databases 16
 
 ################################ SNAPSHOTTING  ################################
 #
 # Save the DB on disk:
 #
 #   save <seconds> <changes>
 #
 #   Will save the DB if both the given number of seconds and the given
 #   number of write operations against the DB occurred.
 #
 #   In the example below the behaviour will be to save:
 #   after 900 sec (15 min) if at least 1 key changed
 #   after 300 sec (5 min) if at least 10 keys changed
 #   after 60 sec if at least 10000 keys changed
 #
 #   Note: you can disable saving at all commenting all the "save" lines.
 #
 #   It is also possible to remove all the previously configured save
 #   points by adding a save directive with a single empty string argument
 #   like in the following example:
 #
 #   save ""
 
 save 900 1
 save 300 10
 save 60 10000
 
 # By default Redis will stop accepting writes if RDB snapshots are enabled
 # (at least one save point) and the latest background save failed.
 # This will make the user aware (in a hard way) that data is not persisting
 # on disk properly, otherwise chances are that no one will notice and some
 # disaster will happen.
 #
 # If the background saving process will start working again Redis will
 # automatically allow writes again.
 #
 # However if you have setup your proper monitoring of the Redis server
 # and persistence, you may want to disable this feature so that Redis will
 # continue to work as usual even if there are problems with disk,
 # permissions, and so forth.
 stop-writes-on-bgsave-error yes
 
 # Compress string objects using LZF when dump .rdb databases?
 # For default that's set to 'yes' as it's almost always a win.
 # If you want to save some CPU in the saving child set it to 'no' but
 # the dataset will likely be bigger if you have compressible values or keys.
 rdbcompression yes
 
 # Since version 5 of RDB a CRC64 checksum is placed at the end of the file.
 # This makes the format more resistant to corruption but there is a performance
 # hit to pay (around 10%) when saving and loading RDB files, so you can disable it
 # for maximum performances.
 #
 # RDB files created with checksum disabled have a checksum of zero that will
 # tell the loading code to skip the check.
 rdbchecksum yes
 
 # The filename where to dump the DB
 dbfilename dump_6391.rdb
 
 # The working directory.
 #
 # The DB will be written inside this directory, with the filename specified
 # above using the 'dbfilename' configuration directive.
 #
 # The Append Only File will also be created inside this directory.
 #
 # Note that you must specify a directory here, not a file name.
 dir /home/liuzhen/data
 
 ################################# REPLICATION #################################
 
 # Master-Slave replication. Use slaveof to make a Redis instance a copy of
 # another Redis server. A few things to understand ASAP about Redis replication.
 #
 # 1) Redis replication is asynchronous, but you can configure a master to
 #    stop accepting writes if it appears to be not connected with at least
 #    a given number of slaves.
 # 2) Redis slaves are able to perform a partial resynchronization with the
 #    master if the replication link is lost for a relatively small amount of
 #    time. You may want to configure the replication backlog size (see the next
 #    sections of this file) with a sensible value depending on your needs.
 # 3) Replication is automatic and does not need user intervention. After a
 #    network partition slaves automatically try to reconnect to masters
 #    and resynchronize with them.
 #
 # slaveof <masterip> <masterport>
 
 # If the master is password protected (using the "requirepass" configuration
 # directive below) it is possible to tell the slave to authenticate before
 # starting the replication synchronization process, otherwise the master will
 # refuse the slave request.
 #
 # masterauth <master-password>
 
 # When a slave loses its connection with the master, or when the replication
 # is still in progress, the slave can act in two different ways:
 #
 # 1) if slave-serve-stale-data is set to 'yes' (the default) the slave will
 #    still reply to client requests, possibly with out of date data, or the
 #    data set may just be empty if this is the first synchronization.
 #
 # 2) if slave-serve-stale-data is set to 'no' the slave will reply with
 #    an error "SYNC with master in progress" to all the kind of commands
 #    but to INFO and SLAVEOF.
 #
 slave-serve-stale-data yes
 
 # You can configure a slave instance to accept writes or not. Writing against
 # a slave instance may be useful to store some ephemeral data (because data
 # written on a slave will be easily deleted after resync with the master) but
 # may also cause problems if clients are writing to it because of a
 # misconfiguration.
 #
 # Since Redis 2.6 by default slaves are read-only.
 #
 # Note: read only slaves are not designed to be exposed to untrusted clients
 # on the internet. It's just a protection layer against misuse of the instance.
 # Still a read only slave exports by default all the administrative commands
 # such as CONFIG, DEBUG, and so forth. To a limited extent you can improve
 # security of read only slaves using 'rename-command' to shadow all the
 # administrative / dangerous commands.
 slave-read-only yes
 
 # Slaves send PINGs to server in a predefined interval. It's possible to change
 # this interval with the repl_ping_slave_period option. The default value is 10
 # seconds.
 #
 # repl-ping-slave-period 10
 
 # The following option sets the replication timeout for:
 #
 # 1) Bulk transfer I/O during SYNC, from the point of view of slave.
 # 2) Master timeout from the point of view of slaves (data, pings).
 # 3) Slave timeout from the point of view of masters (REPLCONF ACK pings).
 #
 # It is important to make sure that this value is greater than the value
 # specified for repl-ping-slave-period otherwise a timeout will be detected
 # every time there is low traffic between the master and the slave.
 #
 # repl-timeout 60
 
 # Disable TCP_NODELAY on the slave socket after SYNC?
 #
 # If you select "yes" Redis will use a smaller number of TCP packets and
 # less bandwidth to send data to slaves. But this can add a delay for
 # the data to appear on the slave side, up to 40 milliseconds with
 # Linux kernels using a default configuration.
 #
 # If you select "no" the delay for data to appear on the slave side will
 # be reduced but more bandwidth will be used for replication.
 #
 # By default we optimize for low latency, but in very high traffic conditions
 # or when the master and slaves are many hops away, turning this to "yes" may
 # be a good idea.
 repl-disable-tcp-nodelay no
 
 # Set the replication backlog size. The backlog is a buffer that accumulates
 # slave data when slaves are disconnected for some time, so that when a slave
 # wants to reconnect again, often a full resync is not needed, but a partial
 # resync is enough, just passing the portion of data the slave missed while
 # disconnected.
 #
 # The biggest the replication backlog, the longer the time the slave can be
 # disconnected and later be able to perform a partial resynchronization.
 #
 # The backlog is only allocated once there is at least a slave connected.
 #
 # repl-backlog-size 1mb
 
 # After a master has no longer connected slaves for some time, the backlog
 # will be freed. The following option configures the amount of seconds that
 # need to elapse, starting from the time the last slave disconnected, for
 # the backlog buffer to be freed.
 #
 # A value of 0 means to never release the backlog.
 #
 # repl-backlog-ttl 3600
 
 # The slave priority is an integer number published by Redis in the INFO output.
 # It is used by Redis Sentinel in order to select a slave to promote into a
 # master if the master is no longer working correctly.
 #
 # A slave with a low priority number is considered better for promotion, so
 # for instance if there are three slaves with priority 10, 100, 25 Sentinel will
 # pick the one with priority 10, that is the lowest.
 #
 # However a special priority of 0 marks the slave as not able to perform the
 # role of master, so a slave with priority of 0 will never be selected by
 # Redis Sentinel for promotion.
 #
 # By default the priority is 100.
 slave-priority 100
 
 # It is possible for a master to stop accepting writes if there are less than
 # N slaves connected, having a lag less or equal than M seconds.
 #
 # The N slaves need to be in "online" state.
 #
 # The lag in seconds, that must be <= the specified value, is calculated from
 # the last ping received from the slave, that is usually sent every second.
 #
 # This option does not GUARANTEES that N replicas will accept the write, but
 # will limit the window of exposure for lost writes in case not enough slaves
 # are available, to the specified number of seconds.
 #
 # For example to require at least 3 slaves with a lag <= 10 seconds use:
 #
 # min-slaves-to-write 3
 # min-slaves-max-lag 10
 #
 # Setting one or the other to 0 disables the feature.
 #
 # By default min-slaves-to-write is set to 0 (feature disabled) and
 # min-slaves-max-lag is set to 10.
 
 ################################## SECURITY ###################################
 
 # Require clients to issue AUTH <PASSWORD> before processing any other
 # commands.  This might be useful in environments in which you do not trust
 # others with access to the host running redis-server.
 #
 # This should stay commented out for backward compatibility and because most
 # people do not need auth (e.g. they run their own servers).
 #
 # Warning: since Redis is pretty fast an outside user can try up to
 # 150k passwords per second against a good box. This means that you should
 # use a very strong password otherwise it will be very easy to break.
 #
 # requirepass foobared
 
 # Command renaming.
 #
 # It is possible to change the name of dangerous commands in a shared
 # environment. For instance the CONFIG command may be renamed into something
 # hard to guess so that it will still be available for internal-use tools
 # but not available for general clients.
 #
 # Example:
 #
 # rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52
 #
 # It is also possible to completely kill a command by renaming it into
 # an empty string:
 #
 # rename-command CONFIG ""
 #
 # Please note that changing the name of commands that are logged into the
 # AOF file or transmitted to slaves may cause problems.
 
 ################################### LIMITS ####################################
 
 # Set the max number of connected clients at the same time. By default
 # this limit is set to 10000 clients, however if the Redis server is not
 # able to configure the process file limit to allow for the specified limit
 # the max number of allowed clients is set to the current file limit
 # minus 32 (as Redis reserves a few file descriptors for internal uses).
 #
 # Once the limit is reached Redis will close all the new connections sending
 # an error 'max number of clients reached'.
 #
 # maxclients 10000
 
 # Don't use more memory than the specified amount of bytes.
 # When the memory limit is reached Redis will try to remove keys
 # according to the eviction policy selected (see maxmemory-policy).
 #
 # If Redis can't remove keys according to the policy, or if the policy is
 # set to 'noeviction', Redis will start to reply with errors to commands
 # that would use more memory, like SET, LPUSH, and so on, and will continue
 # to reply to read-only commands like GET.
 #
 # This option is usually useful when using Redis as an LRU cache, or to set
 # a hard memory limit for an instance (using the 'noeviction' policy).
 #
 # WARNING: If you have slaves attached to an instance with maxmemory on,
 # the size of the output buffers needed to feed the slaves are subtracted
 # from the used memory count, so that network problems / resyncs will
 # not trigger a loop where keys are evicted, and in turn the output
 # buffer of slaves is full with DELs of keys evicted triggering the deletion
 # of more keys, and so forth until the database is completely emptied.
 #
 # In short... if you have slaves attached it is suggested that you set a lower
 # limit for maxmemory so that there is some free RAM on the system for slave
 # output buffers (but this is not needed if the policy is 'noeviction').
 #
 # maxmemory <bytes>
 
 # MAXMEMORY POLICY: how Redis will select what to remove when maxmemory
 # is reached. You can select among five behaviors:
 #
 # volatile-lru -> remove the key with an expire set using an LRU algorithm
 # allkeys-lru -> remove any key accordingly to the LRU algorithm
 # volatile-random -> remove a random key with an expire set
 # allkeys-random -> remove a random key, any key
 # volatile-ttl -> remove the key with the nearest expire time (minor TTL)
 # noeviction -> don't expire at all, just return an error on write operations
 #
 # Note: with any of the above policies, Redis will return an error on write
 #       operations, when there are not suitable keys for eviction.
 #
 #       At the date of writing this commands are: set setnx setex append
 #       incr decr rpush lpush rpushx lpushx linsert lset rpoplpush sadd
 #       sinter sinterstore sunion sunionstore sdiff sdiffstore zadd zincrby
 #       zunionstore zinterstore hset hsetnx hmset hincrby incrby decrby
 #       getset mset msetnx exec sort
 #
 # The default is:
 #
 # maxmemory-policy volatile-lru
 
 # LRU and minimal TTL algorithms are not precise algorithms but approximated
 # algorithms (in order to save memory), so you can select as well the sample
 # size to check. For instance for default Redis will check three keys and
 # pick the one that was used less recently, you can change the sample size
 # using the following configuration directive.
 #
 # maxmemory-samples 3
 
 ############################## APPEND ONLY MODE ###############################
 
 # By default Redis asynchronously dumps the dataset on disk. This mode is
 # good enough in many applications, but an issue with the Redis process or
 # a power outage may result into a few minutes of writes lost (depending on
 # the configured save points).
 #
 # The Append Only File is an alternative persistence mode that provides
 # much better durability. For instance using the default data fsync policy
 # (see later in the config file) Redis can lose just one second of writes in a
 # dramatic event like a server power outage, or a single write if something
 # wrong with the Redis process itself happens, but the operating system is
 # still running correctly.
 #
 # AOF and RDB persistence can be enabled at the same time without problems.
 # If the AOF is enabled on startup Redis will load the AOF, that is the file
 # with the better durability guarantees.
 #
 # Please check http://redis.io/topics/persistence for more information.
 
 appendonly yes
 
 # The name of the append only file (default: "appendonly.aof")
 
 appendfilename "appendonly_6391.aof"
 
 # The fsync() call tells the Operating System to actually write data on disk
 # instead to wait for more data in the output buffer. Some OS will really flush
 # data on disk, some other OS will just try to do it ASAP.
 #
 # Redis supports three different modes:
 #
 # no: don't fsync, just let the OS flush the data when it wants. Faster.
 # always: fsync after every write to the append only log . Slow, Safest.
 # everysec: fsync only one time every second. Compromise.
 #
 # The default is "everysec", as that's usually the right compromise between
 # speed and data safety. It's up to you to understand if you can relax this to
 # "no" that will let the operating system flush the output buffer when
 # it wants, for better performances (but if you can live with the idea of
 # some data loss consider the default persistence mode that's snapshotting),
 # or on the contrary, use "always" that's very slow but a bit safer than
 # everysec.
 #
 # More details please check the following article:
 # http://antirez.com/post/redis-persistence-demystified.html
 #
 # If unsure, use "everysec".
 
 # appendfsync always
 appendfsync everysec
 # appendfsync no
 
 # When the AOF fsync policy is set to always or everysec, and a background
 # saving process (a background save or AOF log background rewriting) is
 # performing a lot of I/O against the disk, in some Linux configurations
 # Redis may block too long on the fsync() call. Note that there is no fix for
 # this currently, as even performing fsync in a different thread will block
 # our synchronous write(2) call.
 #
 # In order to mitigate this problem it's possible to use the following option
 # that will prevent fsync() from being called in the main process while a
 # BGSAVE or BGREWRITEAOF is in progress.
 #
 # This means that while another child is saving, the durability of Redis is
 # the same as "appendfsync none". In practical terms, this means that it is
 # possible to lose up to 30 seconds of log in the worst scenario (with the
 # default Linux settings).
 #
 # If you have latency problems turn this to "yes". Otherwise leave it as
 # "no" that is the safest pick from the point of view of durability.
 
 no-appendfsync-on-rewrite no
 
 # Automatic rewrite of the append only file.
 # Redis is able to automatically rewrite the log file implicitly calling
 # BGREWRITEAOF when the AOF log size grows by the specified percentage.
 #
 # This is how it works: Redis remembers the size of the AOF file after the
 # latest rewrite (if no rewrite has happened since the restart, the size of
 # the AOF at startup is used).
 #
 # This base size is compared to the current size. If the current size is
 # bigger than the specified percentage, the rewrite is triggered. Also
 # you need to specify a minimal size for the AOF file to be rewritten, this
 # is useful to avoid rewriting the AOF file even if the percentage increase
 # is reached but it is still pretty small.
 #
 # Specify a percentage of zero in order to disable the automatic AOF
 # rewrite feature.
 
 auto-aof-rewrite-percentage 100
 auto-aof-rewrite-min-size 64mb
 
 # An AOF file may be found to be truncated at the end during the Redis
 # startup process, when the AOF data gets loaded back into memory.
 # This may happen when the system where Redis is running
 # crashes, especially when an ext4 filesystem is mounted without the
 # data=ordered option (however this can't happen when Redis itself
 # crashes or aborts but the operating system still works correctly).
 #
 # Redis can either exit with an error when this happens, or load as much
 # data as possible (the default now) and start if the AOF file is found
 # to be truncated at the end. The following option controls this behavior.
 #
 # If aof-load-truncated is set to yes, a truncated AOF file is loaded and
 # the Redis server starts emitting a log to inform the user of the event.
 # Otherwise if the option is set to no, the server aborts with an error
 # and refuses to start. When the option is set to no, the user requires
 # to fix the AOF file using the "redis-check-aof" utility before to restart
 # the server.
 #
 # Note that if the AOF file will be found to be corrupted in the middle
 # the server will still exit with an error. This option only applies when
 # Redis will try to read more data from the AOF file but not enough bytes
 # will be found.
 aof-load-truncated yes
 
 ################################ LUA SCRIPTING  ###############################
 
 # Max execution time of a Lua script in milliseconds.
 #
 # If the maximum execution time is reached Redis will log that a script is
 # still in execution after the maximum allowed time and will start to
 # reply to queries with an error.
 #
 # When a long running script exceed the maximum execution time only the
 # SCRIPT KILL and SHUTDOWN NOSAVE commands are available. The first can be
 # used to stop a script that did not yet called write commands. The second
 # is the only way to shut down the server in the case a write commands was
 # already issue by the script but the user don't want to wait for the natural
 # termination of the script.
 #
 # Set it to 0 or a negative value for unlimited execution without warnings.
 lua-time-limit 5000
 
 ################################## SLOW LOG ###################################
 
 # The Redis Slow Log is a system to log queries that exceeded a specified
 # execution time. The execution time does not include the I/O operations
 # like talking with the client, sending the reply and so forth,
 # but just the time needed to actually execute the command (this is the only
 # stage of command execution where the thread is blocked and can not serve
 # other requests in the meantime).
 #
 # You can configure the slow log with two parameters: one tells Redis
 # what is the execution time, in microseconds, to exceed in order for the
 # command to get logged, and the other parameter is the length of the
 # slow log. When a new command is logged the oldest one is removed from the
 # queue of logged commands.
 
 # The following time is expressed in microseconds, so 1000000 is equivalent
 # to one second. Note that a negative number disables the slow log, while
 # a value of zero forces the logging of every command.
 slowlog-log-slower-than 10000
 
 # There is no limit to this length. Just be aware that it will consume memory.
 # You can reclaim memory used by the slow log with SLOWLOG RESET.
 slowlog-max-len 128
 
 ################################ LATENCY MONITOR ##############################
 
 # The Redis latency monitoring subsystem samples different operations
 # at runtime in order to collect data related to possible sources of
 # latency of a Redis instance.
 #
 # Via the LATENCY command this information is available to the user that can
 # print graphs and obtain reports.
 #
 # The system only logs operations that were performed in a time equal or
 # greater than the amount of milliseconds specified via the
 # latency-monitor-threshold configuration directive. When its value is set
 # to zero, the latency monitor is turned off.
 #
 # By default latency monitoring is disabled since it is mostly not needed
 # if you don't have latency issues, and collecting data has a performance
 # impact, that while very small, can be measured under big load. Latency
 # monitoring can easily be enalbed at runtime using the command
 # "CONFIG SET latency-monitor-threshold <milliseconds>" if needed.
 latency-monitor-threshold 0
 
 ############################# Event notification ##############################
 
 # Redis can notify Pub/Sub clients about events happening in the key space.
 # This feature is documented at http://redis.io/topics/notifications
 #
 # For instance if keyspace events notification is enabled, and a client
 # performs a DEL operation on key "foo" stored in the Database 0, two
 # messages will be published via Pub/Sub:
 #
 # PUBLISH __keyspace@0__:foo del
 # PUBLISH __keyevent@0__:del foo
 #
 # It is possible to select the events that Redis will notify among a set
 # of classes. Every class is identified by a single character:
 #
 #  K     Keyspace events, published with __keyspace@<db>__ prefix.
 #  E     Keyevent events, published with __keyevent@<db>__ prefix.
 #  g     Generic commands (non-type specific) like DEL, EXPIRE, RENAME, ...
 #  $     String commands
 #  l     List commands
 #  s     Set commands
 #  h     Hash commands
 #  z     Sorted set commands
 #  x     Expired events (events generated every time a key expires)
 #  e     Evicted events (events generated when a key is evicted for maxmemory)
 #  A     Alias for g$lshzxe, so that the "AKE" string means all the events.
 #
 #  The "notify-keyspace-events" takes as argument a string that is composed
 #  by zero or multiple characters. The empty string means that notifications
 #  are disabled at all.
 #
 #  Example: to enable list and generic events, from the point of view of the
 #           event name, use:
 #
 #  notify-keyspace-events Elg
 #
 #  Example 2: to get the stream of the expired keys subscribing to channel
 #             name __keyevent@0__:expired use:
 #
 #  notify-keyspace-events Ex
 #
 #  By default all notifications are disabled because most users don't need
 #  this feature and the feature has some overhead. Note that if you don't
 #  specify at least one of K or E, no events will be delivered.
 notify-keyspace-events ""
 
 ############################### ADVANCED CONFIG ###############################
 
 # Hashes are encoded using a memory efficient data structure when they have a
 # small number of entries, and the biggest entry does not exceed a given
 # threshold. These thresholds can be configured using the following directives.
 hash-max-ziplist-entries 512
 hash-max-ziplist-value 64
 
 # Similarly to hashes, small lists are also encoded in a special way in order
 # to save a lot of space. The special representation is only used when
 # you are under the following limits:
 list-max-ziplist-entries 512
 list-max-ziplist-value 64
 
 # Sets have a special encoding in just one case: when a set is composed
 # of just strings that happens to be integers in radix 10 in the range
 # of 64 bit signed integers.
 # The following configuration setting sets the limit in the size of the
 # set in order to use this special memory saving encoding.
 set-max-intset-entries 512
 
 # Similarly to hashes and lists, sorted sets are also specially encoded in
 # order to save a lot of space. This encoding is only used when the length and
 # elements of a sorted set are below the following limits:
 zset-max-ziplist-entries 128
 zset-max-ziplist-value 64
 
 # HyperLogLog sparse representation bytes limit. The limit includes the
 # 16 bytes header. When an HyperLogLog using the sparse representation crosses
 # this limit, it is converted into the dense representation.
 #
 # A value greater than 16000 is totally useless, since at that point the
 # dense representation is more memory efficient.
 #
 # The suggested value is ~ 3000 in order to have the benefits of
 # the space efficient encoding without slowing down too much PFADD,
 # which is O(N) with the sparse encoding. The value can be raised to
 # ~ 10000 when CPU is not a concern, but space is, and the data set is
 # composed of many HyperLogLogs with cardinality in the 0 - 15000 range.
 hll-sparse-max-bytes 3000
 
 # Active rehashing uses 1 millisecond every 100 milliseconds of CPU time in
 # order to help rehashing the main Redis hash table (the one mapping top-level
 # keys to values). The hash table implementation Redis uses (see dict.c)
 # performs a lazy rehashing: the more operation you run into a hash table
 # that is rehashing, the more rehashing "steps" are performed, so if the
 # server is idle the rehashing is never complete and some more memory is used
 # by the hash table.
 #
 # The default is to use this millisecond 10 times every second in order to
 # active rehashing the main dictionaries, freeing memory when possible.
 #
 # If unsure:
 # use "activerehashing no" if you have hard latency requirements and it is
 # not a good thing in your environment that Redis can reply form time to time
 # to queries with 2 milliseconds delay.
 #
 # use "activerehashing yes" if you don't have such hard requirements but
 # want to free memory asap when possible.
 activerehashing yes
 
 # The client output buffer limits can be used to force disconnection of clients
 # that are not reading data from the server fast enough for some reason (a
 # common reason is that a Pub/Sub client can't consume messages as fast as the
 # publisher can produce them).
 #
 # The limit can be set differently for the three different classes of clients:
 #
 # normal -> normal clients including MONITOR clients
 # slave  -> slave clients
 # pubsub -> clients subscribed to at least one pubsub channel or pattern
 #
 # The syntax of every client-output-buffer-limit directive is the following:
 #
 # client-output-buffer-limit <class> <hard limit> <soft limit> <soft seconds>
 #
 # A client is immediately disconnected once the hard limit is reached, or if
 # the soft limit is reached and remains reached for the specified number of
 # seconds (continuously).
 # So for instance if the hard limit is 32 megabytes and the soft limit is
 # 16 megabytes / 10 seconds, the client will get disconnected immediately
 # if the size of the output buffers reach 32 megabytes, but will also get
 # disconnected if the client reaches 16 megabytes and continuously overcomes
 # the limit for 10 seconds.
 #
 # By default normal clients are not limited because they don't receive data
 # without asking (in a push way), but just after a request, so only
 # asynchronous clients may create a scenario where data is requested faster
 # than it can read.
 #
 # Instead there is a default limit for pubsub and slave clients, since
 # subscribers and slaves receive data in a push fashion.
 #
 # Both the hard or the soft limit can be disabled by setting them to zero.
 client-output-buffer-limit normal 0 0 0
 client-output-buffer-limit slave 256mb 64mb 60
 client-output-buffer-limit pubsub 32mb 8mb 60
 
 # Redis calls an internal function to perform many background tasks, like
 # closing connections of clients in timeout, purging expired keys that are
 # never requested, and so forth.
 #
 # Not all tasks are performed with the same frequency, but Redis checks for
 # tasks to perform accordingly to the specified "hz" value.
 #
 # By default "hz" is set to 10. Raising the value will use more CPU when
 # Redis is idle, but at the same time will make Redis more responsive when
 # there are many keys expiring at the same time, and timeouts may be
 # handled with more precision.
 #
 # The range is between 1 and 500, however a value over 100 is usually not
 # a good idea. Most users should use the default of 10 and raise this up to
 # 100 only in environments where very low latency is required.
 hz 10
 
 # When a child rewrites the AOF file, if the following option is enabled
 # the file will be fsync-ed every 32 MB of data generated. This is useful
 # in order to commit the file to the disk more incrementally and avoid
 # big latency spikes.
 aof-rewrite-incremental-fsync yes

redis_6391.conf源码

(7) 重启指定端口的服务，例如此处在Redis按照src目录下，运行./redis-server redis_6391.conf即可启动服务，待服务完成启动成功后，即可把指定的AOF文件数据加载进去（PS：此步骤需要先确认指定目录下的AOF文件已被替换成目标AOF文件，期间可以多次重启实现具体AOF文件加载）

以下给出我本机使用Redis加载启动大小为1.7G的aof文件，由于文件比较大，所以加载的时间有点长，此处是加载了60秒。

liuzhen@liuzhen-ubuntu:~/redis-2.8.17/src$ ./redis-server redis_6391.conf
 
[68180] 19 Jul 15:02:07.997 * Increased maximum number of open files to 10032 (it was originally set to 1024).
 
                _._                                                  
 
           _.-``__ ''-._                                             
 
      _.-``    `.  `_.  ''-._           Redis 2.8.17 (00000000/0) 64 bit
 
  .-`` .-```.  ```\/    _.,_ ''-._                                   
 
 (    '      ,       .-`  | `,    )     Running in stand alone mode
 
 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6391
 
 |    `-._   `._    /     _.-'    |     PID: 68180
 
  `-._    `-._  `-./  _.-'    _.-'                                   
 
 |`-._`-._    `-.__.-'    _.-'_.-'|                                  
 
 |    `-._`-._        _.-'_.-'    |           http://redis.io        
 
  `-._    `-._`-.__.-'_.-'    _.-'                                   
 
 |`-._`-._    `-.__.-'    _.-'_.-'|                                  
 
 |    `-._`-._        _.-'_.-'    |                                  
 
  `-._    `-._`-.__.-'_.-'    _.-'                                   
 
      `-._    `-.__.-'    _.-'                                       
 
          `-._        _.-'                                           
 
              `-.__.-'                                               
 
[68180] 19 Jul 15:02:08.011 # Server started, Redis version 2.8.17
 
[68180] 19 Jul 15:05:12.843 * DB loaded from append only file: 184.831 seconds
 
[68180] 19 Jul 15:05:12.843 * The server is now ready to accept connections on port 6391
 
[68180] 19 Jul 15:05:13.008 * 10000 changes in 60 seconds. Saving...
 
[68180] 19 Jul 15:05:13.084 * Background saving started by pid 68228
 
[68228] 19 Jul 15:05:47.548 * DB saved on disk
 
[68228] 19 Jul 15:05:47.613 * RDB: 23 MB of memory used by copy-on-write
 
[68180] 19 Jul 15:05:47.717 * Background saving terminated with success
 
[68180] 19 Jul 15:07:54.064 * DB saved on disk
 
[68180] 19 Jul 15:08:58.096 * Asynchronous AOF fsync is taking too long (disk is busy?). Writing the AOF buffer without waiting for fsync to complete, this may slow down Redis.
 
[68180] 19 Jul 16:49:14.515 * Background saving started by pid 90980
 
[90980] 19 Jul 16:56:56.883 * DB saved on disk
 
[90980] 19 Jul 16:56:56.966 * RDB: 4 MB of memory used by copy-on-write
 
[68180] 19 Jul 16:56:57.418 * Background saving terminated with success

(8)打开Redis客户端，运行./redis-cli -p 6391,客户端启动成功后，运行命令save，等待命令运行成功后，即可得到本步骤最终目标的RDB持久化文件（PS：此处如果是在线上环境尝试，建议采用bgsave命令）

此处给出，使用AOF文件还原数据后，查看具体数据信息的结果：

liuzhen@liuzhen-ubuntu:~/redis-2.8.17/src$ ./redis-cli -p 6391
 
127.0.0.1:6391> info
 
# Server
 
redis_version:2.8.17
 
redis_git_sha1:00000000
 
redis_git_dirty:0
 
redis_build_id:4ba260b6ab802599
 
redis_mode:standalone
 
os:Linux 4.13.0-39-generic x86_64
 
arch_bits:64
 
multiplexing_api:epoll
 
gcc_version:5.4.0
 
process_id:68180
 
run_id:97cddc494e3924885bacb03776dfe09e8fa055f9
 
tcp_port:6391
 
uptime_in_seconds:9400
 
uptime_in_days:0
 
hz:10
 
lru_clock:5266472
 
config_file:/home/liuzhen/redis-2.8.17/src/redis_6391.conf
 
# Clients
 
connected_clients:1
 
client_longest_output_list:0
 
client_biggest_input_buf:0
 
blocked_clients:0
 
# Memory
 
used_memory:2239514040
 
used_memory_human:2.09G
 
used_memory_rss:330895360
 
used_memory_peak:2272377648
 
used_memory_peak_human:2.12G
 
used_memory_lua:38912
 
mem_fragmentation_ratio:0.15
 
mem_allocator:jemalloc-3.6.0
 
# Persistence
 
loading:0
 
rdb_changes_since_last_save:0
 
rdb_bgsave_in_progress:0
 
rdb_last_save_time:1531990617
 
rdb_last_bgsave_status:ok
 
rdb_last_bgsave_time_sec:463
 
rdb_current_bgsave_time_sec:-1
 
aof_enabled:1
 
aof_rewrite_in_progress:0
 
aof_rewrite_scheduled:0
 
aof_last_rewrite_time_sec:-1
 
aof_current_rewrite_time_sec:-1
 
aof_last_bgrewrite_status:ok
 
aof_last_write_status:ok
 
aof_current_size:1700508277
 
aof_base_size:1699947297
 
aof_pending_rewrite:0
 
aof_buffer_length:0
 
aof_rewrite_buffer_length:0
 
aof_pending_bio_fsync:0
 
aof_delayed_fsync:1
 
# Stats
 
total_connections_received:2
 
total_commands_processed:281
 
instantaneous_ops_per_sec:0
 
rejected_connections:0
 
sync_full:0
 
sync_partial_ok:0
 
sync_partial_err:0
 
expired_keys:9290
 
evicted_keys:0
 
keyspace_hits:1065050
 
keyspace_misses:0
 
pubsub_channels:0
 
pubsub_patterns:0
 
latest_fork_usec:101807
 
# Replication
 
role:master
 
connected_slaves:0
 
master_repl_offset:0
 
repl_backlog_active:0
 
repl_backlog_size:1048576
 
repl_backlog_first_byte_offset:0
 
repl_backlog_histlen:0
 
# CPU
 
used_cpu_sys:46.01
 
used_cpu_user:189.71
 
used_cpu_sys_children:134.11
 
used_cpu_user_children:79.12
 
# Keyspace
 
db1:keys=1146336,expires=51965,avg_ttl=276142509
 
127.0.0.1:6391>

备注：在Redis指定端口服务加载给定的AOF文件时，如果AOF文件过大，系统可能会报如下错误：

Can't save in background: fork: Cannot allocate memory

解决办法：

修改系统/etc/sysctl.conf文件，并添加以下内容：

vm.overcommit_memory=1

在 FreeBSD上:

sudo /etc/rc.d/sysctl reload

在 Linux上:

sudo sysctl -p /etc/sysctl.conf

---

参考资料：

• 1.redis中的数据快照、AOF、数据恢复、主从复制介绍及使用（https://blog.csdn.net/zhu_xun/article/details/16806697）
• 2.redis如何利用appendonly.aof恢复数据（https://blog.csdn.net/sanbingyutuoniao123/article/details/50484674）
• 3.Redis持久存储(AOF/Snapshot)（http://shift-alt-ctrl.iteye.com/blog/1878716）
• 4.redis dump.rdb appendonly.aof 文件路径修改（https://blog.csdn.net/yangxujia/article/details/51010222）
• 5.超大数据快速导入MySQL（https://blog.csdn.net/dingding_12345/article/details/78646484）
• 6.redis Can’t save in background: fork: Cannot allocate memory 解决及原理（https://blog.csdn.net/zqz_zqz/article/details/53384854）
• 7.redis bgsave failed because fork Cannot allocate memory（https://stackoverflow.com/questions/11752544/redis-bgsave-failed-because-fork-cannot-allocate-memory）
• 8.《Redis设计与实现 第二版》  黄健宏 著